Revisiting the NH3-SCR performance of MnO2 with different crystal phases: From electronic structure to catalytic activity

• Published in: Applied catalysis. B, Environmental Vol. 380; p. 125753
• Main Authors: Yue, Yi, Xiong, Shangchao, Ou, Hongjun, Yang, Yi, Sun, Xiaoyu, Wang, Houlin, Xi, Yingwei, Gong, Zhengjun, Chen, Jianjun, Li, Junhua
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2026
• Subjects: Electronic structure; Low-temperature catalysts; MnO2; NH3-SCR; NOx; Reaction mechanism; MnO2; Reaction mechanism; NH3-SCR; Electronic structure; NOx; Low-temperature catalysts
• ISSN: 0926-3373
• DOI: 10.1016/j.apcatb.2025.125753

Manganese oxides are among the most promising low-temperature NH3-selective catalytic reduction (NH3-SCR) catalysts. MnO2 with different crystal phases (α-, β-, γ-, and δ-MnO2) exhibits significantly different NH3-SCR performance. The fundamental factors influencing the activity of MnO2 with different crystal phases remain a subject of considerable debate. This study finds that β- and δ-MnO2 show poor activity due to low reactivity and poor NH3 adsorption. In contrast, α- and γ-MnO2 show high activity but differ in optimal reaction temperature windows. The smaller Mn-O coordination number and longer Mn-O bond distance in α-MnO2 result in an upward shift of its d-band center. Therefore, α-MnO2 exhibits stronger coupling between the Mn-d and N-p orbitals during NH3 adsorption, promoting *NH3 activation. As a result, α-MnO2 outperforms γ-MnO2 in low-temperature catalytic activity. This study reveals the impact of microscopic electronic orbital coupling on macroscopic catalytic performance, providing new insights for developing advanced low-temperature NH3-SCR catalysts. [Display omitted] •Coordination environments cause SCR performance differences in MnO2 crystal phases.•d-Band shifts lead to varied NH3 activation barriers in α- and γ-MnO2.•Poor redox ability at low temperature makes β-MnO2 catalytically less active.•Nitrate buildup on δ-MnO2 inhibits SCR performance.